This application relates to magnetic disc drives and more particularly to a disc drive clamping ring for securing information storage disc within the disc drive.
Disc drives are data storage devices that store digital data in magnetic form on a storage medium on a rotating information storage disc. Modern disc drives include one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g., a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move across the surfaces of the discs.
A typical spindle motor assembly includes a rotating spindle hub journaled to a non-rotating spindle shaft. The spindle hub is cylindrical and has an inside wall that supports a permanent magnet and yoke that forms the rotor of the spindle motor. A disc mounting flange extends from the bottom of the spindle hub to provide a support surface for a plurality of alternatingly stacked information storage discs and discs spacers. A disc clamp is typically secured to the rotating spindle hub via a plurality of screws so as to exert a vertical clamping force onto the disc stack and secure the disc stack to the spindle hub.
A presistant problem within the disc drive industry is having sufficient frictional force within the disc stack, i.e, friction between the information storage discs and disc spacers, the disc clamp and the disc mounting flange, to avoid radial/lateral shifting of the information storage discs (disc slip) relative to the spindle hub. Disc slip results in disturbances in the accuracy of reading and writing information to and from the information storage disc. Disc slip is typically avoided when the frictional forces within the disc stack are greater than the lateral load on the disc stack.
The lateral load on an information storage disc is dependent on both the acceleration speeds of the disc drive and on mechanical shock events felt by the disc drive. Recent developments within the disc drive industry have exacerbated both of these parameters, spindle motor rotation speeds are increasing, and portable laptop computers, more prone to mechanical shock events, have become prevalent. As such, there is a need in the industry to offset increases in the lateral force felt within the disc stack with corresponding increases in the frictional forces felt within the disc stack, thereby avoiding disc slip.
Typically, the frictional force within the disc stack is dependent on the frictional coefficients between the components of the disc stack and the vertical clamping load imparted to the disc stack by the disc clamp. As such, one solution for offsetting increased lateral loads within the disc stack is to increase the vertical clamping load exerted on the disc stack by the disc clamp. Increasing the vertical clamping load on the disc stack generally entails the further increase of torque on the screws that secure the disc clamp to the spindle hub, and so increasing the vertical force exerted by the disc clamp on the inner diameter of the top information storage disc. However, increasing the torque on the screws has several shortcomings, for instance, increased torque results in stripping of the screw hole threads in the spindle hub and galling. Further, because of the industry trend toward decreased information storage disc thickness, the amount of vertical clamping force that can be applied to an information storage disc without causing mechanical distortions has reached its useful limit.
In light of these facts, it is believed that a continued attempt to offset increases in the lateral load on the disc stack through increases in the vertical clamping force on the disc stack is, or soon will, have reached its maximum useful extreme. Therefore, there is a need in the relevant art to overcome increased lateral forces on the disc stack without relying on any substantial increases in the vertical clamping force. Against this backdrop the present invention has been developed.
The present invention is an apparatus and method for securing information storage discs onto a spindle hub of a spindle motor.
In accordance with a preferred embodiment of the present invention, a spindle hub assembly has a spindle hub that defines a cylindrical sidewall for receiving an information storage disc. The information storage disc has an inner edge that defines a central aperture which is passed over the spindle hub so that the inner edge of the information storage disc is spaced away from the spindle hub sidewall. A serpentine shaped clamping ring is sandwiched between the spindle hub sidewall and the inner edge of the information storage disc for applying a distributed radial load to the information storage disc.
The present invention can further be implemented as a method for securing an information storage disc within a disc drive. The method includes the steps of forming a clamping ring having a predetermined number of serpentine shaped curves, curling the clamping ring to a diameter smaller than a diameter of an inner edge of the information storage disc, positioning the curled clamping ring inside the inner edge of the information storage disc, unfurling the clamping ring to exert an outward force on the inner edge of the information storage disc and positioning the information storage disc on the sidewall of the spindle hub so that the clamping ring exerts a radial load against the information storage disc.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.